Choledochal Cyst Type I

A 6-year-old girl presents with a 4-month history of intermittent right upper quadrant pain, a palpable abdominal mass, and recurrent episodes of jaundice with dark urine and pale stools. Abdominal ultrasound with color Doppler shows a 5.8 cm fusiform cystic dilatation of the extrahepatic common bile duct (marked **A** in the diagram), with normal intrahepatic biliary radicles and a normal-caliber cystic duct. MRCP confirms an anomalous pancreaticobiliary ductal junction with a 20 mm common channel. Which of the following is the most appropriate definitive management for this condition?